Iliac connector, connector head, spinal fixation system and method of stabilizing a spine

ABSTRACT

An inventive iliac connector comprises a connector head ( 1 ) and a connecting rod ( 2 ) for connecting a sacrum (S) or a spine (SP) to an ilium (I). The connector head ( 1 ) has a first hole ( 15 ) for holding a spinal rod ( 3 ) and a second hole ( 16 ) for holding the connecting rod ( 2 ), wherein the connecting rod ( 2 ) is made of a material being more flexible than titanium. This iliac connector enables a stabilization of ilium, sacrum and spine and enables at the same time movement between ilium and sacrum.

This patent application claims priority of US provisional applicationno. 61/644,689 filed on May 9, 2012. The present invention is in thefield of stabilization and fixation of a spine.

TECHNICAL FIELD Prior Art

Several fixation techniques are known for the treatment of spinaldeformities and pathologies, among them spinal fusion. While this is anextensive operation with potentially serious complications, a spinalfusion can be considered a lesser evil than the problem the surgeon mustsolve. The diseased spinal segments of a patient may be so unstable,painful and potentially nerve damaging that blocking mobile spinesegments to form one bone is thought to be the best method of treatment.To fix the spine, surgeons attach one or more longitudinal fixationelements, such as rods or plates, to the spine at several fixation sitesusing bone screws. Often spinal bone screws are fixed through one of themost solid sections of a vertebrae, the pedicle.

The vertebral pedicles connect the anterior vertebral body to itsposterior elements where the actuating back muscles are attached. Thepedicles at each motion segment work like a lever between the back andthe front of the spine. They mediate almost all the forces from the backmuscles to the anterior spine, enabling the human being to stand erectand to bend forward in a controlled manner. From the cervical to thelumbar spine that stops adjacent to the sacrum, the pedicle is the mostsolid structure to place a screw that is connected by a longitudinalelement that fixes motion segments of the spine.

EP 1 238 637 discloses a well-working longitudinal implant fastened onbones on either side of a damaged area of the spine. Pedicle bone screwsare used for the fixation. The longitudinal implant is a carbon filamentcomposite material, wherein the filament is encapsulated in a polymermatrix. The material is known on the market as ostaPek.

Sometimes, a surgeon must extend a long fusion beyond the lumbar spineand connect it to the sacrum where the bone is soft and spongy. At endof a long fusion construct, the implant forms a long lever arm thatworks to pull the screws from this soft sacral bone.

To prevent a screw pull-out from the sacrum and a fusion-constructfailure, it is known to increase the anchor locations. This can be donewith multiple screws in the sacrum. It is also known to extend theentire construct lateral, crossing the sacral iliac joint to engage theiliac bone as well.

U.S. Pat. No. 5,133,717 shows a sacral support saddle for fastening aspinal rod to the sacrum.

U.S. Pat. No. 5,593,407 suggests to connect the lowest lumbar vertebradirectly to the ilium, using a bent rod and pedicle screws.

US 2012/0022595 describes a sacral-iliac stabilization system with asacral-iliac plate having a first screw hole for receiving a firstfastener to secure the iliac portion to the iliac bone. A second andthird screw hole is also provided for receiving a second and a thirdfastener to secure the sacral portion to the sacral bone. US2006/0106382 also discloses a plate connecting the sacrum to the ilium.US 2008/0154306 suggests using long screws to connect the sacrum to theilium.

US 2008/0021456 shows a quite complicated system comprising a plate onthe ilium, rod like connectors to the sacrum and a stabilization platebetween the lowest lumbar vertebra and the sacrum.

US 2008/0021455 discloses a sacral-iliac cross connector to allow forcoupling of the connector to a spinal fixation rod and anchors. Theconnector has a receiver head with opposed sidewalls defining a seatingportion for an insert which is configured to seat a spinal rod. Theconnector also includes a connecting rod with a flat end part comprisinga hole. This end part is held in a slot on the bottom side of theseating portion and it is fixed to a post or shaft arranged on thebottom side of the insert. Therefore, the connecting rod has to bearranged and fixed before the spinal rod can be placed into the insertand fixed therein.

US 2008/0021454, which refers to US 2008/0021455, shows in FIG. 5A aspine fixation system with a spinal rod, a sacral-iliac cross connectorcomprising a connector rod and a plate fixed on the ilium.

However, the loss of the sacral-iliac joint is very much noticed by thepatient when blocked. The reason for this is the following:

The pelvis comprises three bony parts (two iliac bones and the sacrum).Together the iliac bones and sacrum form a ring, with the iliac bonesjoined anterior at the pubis and the sacrum placed posterior betweeniliac bones like a keystone. The pelvic ring is held together by amultitude of complex ligaments. These ligaments allow small movement,particularly at the sacro-iliac joints, that are paired left and rightbetween the sacrum and the pelvis. With their ligaments, thesacral-iliac joints allow a subtle nodding movement of the sacrumbetween the iliac bones at all changes in posture. This slightly changesthe form of the pelvic ring during forward bending (flexion) andbackward bending (extension). In this manner, this subtle sacralmovement and change in pelvic form become a mechanism that absorbsenergy propagated from the limbs to the spine and vice versa. Thismechanism is often unnoticed by the patient until it is disrupted orgone.

Sacral-iliac fixations, designed to prevent screw pull out from thesacrum, also eliminate the ability of the sacral-iliac joint to gentlyflex and nod in a normal manner, which allow certain postures and energyabsorbtion between the lower and upper body. Since the posteriorligaments are removed and the joint blocked, a minute, but yetsignificant motion is lost. All energy is driven into the spine from thepelvis and sacrum that has become one bone. Shocks can not be absorbedcorrectly. Shocks are uncomfortable and over time can degenerate thesurrounding joints of the hips and spine.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to allow a stabilization ofthe iliac area while still enabling a natural movement between ilium andsacrum.

The inventive iliac connector comprises a connector head and an elongateconnecting member for connecting a sacrum or a spine to an ilium. Theconnector head has a first hole for holding an elongate spinal memberand a second hole for holding the elongate connecting member, whereinthe elongate connecting member is made of a material being more flexiblethan titanium. Preferably, the elongate connecting member is made of amaterial less flexible than a rope or a rubber band.

At least one of the elongate connecting member and the elongate spinalmember, preferably both, are rods. In the following the expression “rod”will be use, wherein other shapes are meant as well.

Since the connecting rod is more flexible than titanium, movement of theilium relative to the sacrum is still possible. However the rod givessufficient stabilization between these two parts. The rod allows a verylow deformation in longitudinal direction but still allows sufficientbending and rotation around its longitudinal direction. It also allows,when coupled with a spinal rod a coupled motion.

This spinal fixation system applies a corrective force upon the spine,but does also allow some deflection, returning resiliently due to theinherent memory of form that is desired by the surgeon as the patientmoves and as normal body stress are exerted upon it. This spinalfixation system is elastic enough to allow stress to pass throughadjacent and connected bones that will encourage bone growth and thenreturn to the original corrective form while at the same time it is notso flexible as to over stress the bone and cause micro stress fractures.

The rod can be straight or curved in its initial position without anyforce applied to it.

In a preferred embodiment, the connecting rod is made of a filamentcomposite material, preferably with long strands or filaments.Preferably the filaments are carbon filaments. The filaments arepreferably oriented, thereby extending mainly in longitudinal directionof the connecting rod. Preferably, the filaments are woven. A matrixpreferably holds the carbon strands in place when load passes throughthe carbon fibers, while at the same time, allows some matrix stretchingbetween the fibers. This brings flexibility and spring-like qualities tothe rod in bending as well as torsion. Preferably, the connecting rod isa composite rod as described in EP 1 238 637.

The rod can have the same fiber orientation and matrix arrangementthroughout the whole length of the connecting rod. However theconnecting rod can also have different orientation of the fibers atdifferent locations in the rod to make it stronger, stiffer or moreflexible at these different locations. A disclosure of such a rod can befound in US 2008/026548.

In a preferred embodiment, the carbon filaments are encapsulated in apolymer matrix, the matrix being preferablypolyether-ketoneetherketoneketone (PEKEKK) or polyetheretherketone(PEEK).

In a preferred embodiment, the connecting rod has throughout its wholelength a non-changing outer geometry, even when the stiffness of the rodchanges throughout its length. Preferably, the rod has a roundcross-section. It can also have other shapes, such as a polygonalcross-section. This simplifies production as well as surgery, since therod can be manufactured in standard lengths and it can be cut for eachapplication individually.

It is a further advantage of the inventive iliac connector that the rodis made of a radio lucent material. This enables the surgeon to analyzetissue and bone beneath the iliac connector, to observe bone formationor detect other pathologies at a later time.

The invention also refers to a special connector head, which can forexample be used in the inventive iliac connector. This connector headhas a first hole defining a first central axis for holding a spinal rodand a second hole defining a central second axis for holding aconnecting rod, the two central axes extending in different directionsand at a distance to each other. Each hole is in communication with aseparate fixation opening, the fixation openings being arranged suchthey allow mounting of the connecting rod and the spinal rodindependently from each other. This connector head can hold two rods,i.e. a spinal rod and a connecting rod, individually. It does not dependwhich one is fixed first within the connector head. An already fixed rodcan also made loose again without manipulation of the other rod. Thesurgeon has therefore utmost ability to adapt the fixation to the localanatomy and to the goals for treatment. For example, the two rods can beplaced in any order, secured in any sequence that is optimal forprecision in placement, for the ease of assembly and to placeprogressive forces to better align the spine

This connector head is preferably used with this stiff and flexible rodmentioned above. However it can also be used with other rods, forexample rods known in the state of the art which are used for spinalcorrections. It can also be used for combining to other kind of rods,not only as iliac connector.

Preferably, the first central axis of the first hole and the secondcentral axis of the second hole extend in two planes extending at adistance from each other but parallel to each other. However, it is alsopossible that these two planes are arranged in an angle to each other,i.e. one of the holes being tilted with respect to the other hole.

In a preferred embodiment, the fixation opening of the first hole isarranged at an angle α different from 90° to the fixation opening of thesecond hole. This makes both fixation openings easily accessible for thesurgeon. Preferred angles are between 70° to 30°, more preferablybetween 60° to 40°. In one example the angle α is about 60°. Inpreferred embodiments the angle α is about 45° or less. In anotherpreferred embodiment, this angle is approximately 0°.

The connector head preferably comprises two side walls, a rear wall, afront wall, a bottom and a top, wherein the first hole is arranged inone of the side walls, the second hole is arranged in the rear wall, thefirst fixation opening is arranged in the front wall and the secondfixation opening is arranged in the top. This arrangement allowsminimizing the size of the connector head. Preferably, the back wall isperpendicular to the side walls and the top is perpendicular to the rearwall and the side walls. The side walls can be parallel to each other.Preferably, the edges between the walls are rounded.

In a preferred embodiment, the front wall comprises at least one sectionwhich is inclined with respect to the rear wall. The first fixationopening is arranged in the inclined section. This minimizes the size ofthe connector head even more and allows a good access to the fixationopenings.

The size is further minimized and optimized to local conditions when atransition area connecting the back wall and the bottom has a roundedouter shape.

Preferably, at least some, preferably all of the following walls areplane: the side walls, the rear wall, the front wall and the top.

In another preferred embodiment of the connector head, the firstfixation opening is arranged in a first surface of the connector headand the second fixation opening is arranged in a second surface of theconnector head, wherein the first surface extends in a plane parallelbut at a distance to a plane defined by the second surface. This allowsa good access to the fixation openings and places the head further awayfrom the skin to create a less prominent implant construct.

Access and size are also optimized when the connector head comprises afirst body with a cube-like shape and a second body with a cube-likeshape, the first body comprising the first hole and the first fixationopening and the second body comprising the second hole and the secondfixation opening, wherein the first body is arranged staggered below thesecond body.

A connector head comprising the features of both paragraphs mentionedabove has been found to be a preferred embodiment.

The first and second holes can be blind holes. Preferably, at least oneand most preferably both of them are straight through holes. The firsthole preferably extends from a first of the side walls to a second ofthe side walls and the second hole extends from the rear wall to thefront wall. The spinal rod and the connecting rod can thereforepenetrate the connector head and the surgeon has during operation utmostability to define the length of the clamped parts of the rods, the rodsbeing clamped between connector head and the anchors, for example thepedicle bone screws.

Preferably, the spinal rod and/or the connecting rod are firmly, i.e.fixedly held in the connector head. Preferably, both of them are firmlyheld within the connector heads, not allowing any lateral, longitudinalor rotational rod movement at their fixation points.

The above mentioned connector is preferably used in a spinal fixationsystem, wherein this system further comprises a spinal rod made of amaterial being more flexible than titanium, spinal bone screws andpreferably at least one sacral bone screw being penetrated by thisspinal rod. The spinal rod is hold in the iliac connector head. At leastone iliac bone screw can be present fixed in the ilium, wherein theconnecting rod of the iliac connector is held in the at least one iliacbone screw. Preferably, the spinal rod and the connecting rod are madeof the same material, especially the one described above. This systemallows the stabilization of the spine and the ilium thereby allowingsome movement between ilium and sacrum.

Preferably the system uses fixation screws into the sacrum as well,therefore fixing the spinal rod to the sacrum and connecting the sacrumwith the ilium using the inventive iliac connector. However it is alsopossible to connect the lowest lumbar vertebra directly to the ilium byusing the inventive connector.

The inventive system maintains some movement at the sacral-iliac jointby placing spinal rod and connecting rod at an angle to each other,preferably almost perpendicular to one another, wherein at least theconnecting rod is made of a material being more flexible than titanium.Preferably, the rods are made of a composite material comprising fibresoriented in longitudinal direction of the rod, so that the fibres of thedifferent rods are oriented at an angle, preferably about 90° to eachother, for example 84°.

The connecting rod works in rotation and with some bending making acoupled movement, while the spinal rod preferably works in flexion andextension as well as some torsion of the spine. This system more closelyapproximates the function of the posterior sacral-iliac ligaments, whileat the same time preventing pull out of the screws at the sacrum. Italso absorbs shocks better by allowing a minute but significant movementof the sacrum between the iliac bones of the pelvis during flexion(forward bending) and extension (backward bending). In addition stressshielding and the possible consequence of osteoporosis is avoided in thepelvis and sacrum.

This system is more comfortable for the patient; it protects thesurrounding hips and spine that are adjacent to the fusion construct,and prevents screw pull out and construct failure at the sacrum.

The inventive method for stabilizing a spine comprises the steps of

-   -   a) accessing the sacrum and iliac portions of the spine;    -   b) fixing an elongate spinal member with at least one spinal        bone screw to at least one pedicle of the spine, the elongate        spinal member having a first end;    -   c) fixing an elongate connecting member with a iliac bone screw        to the iliac, the elongate connecting member having a second end        and    -   d) fixing the first end of the elongate spinal member and the        second end of the elongate connecting member relative to each        other at an angle of about 90°, wherein the chronology of        fixation of the first end the second end can be chosen by the        surgeon.

In a preferred variant, the method further comprises the step of fixingthe elongate spinal member with at least one, preferably exactly onesacral bone screw to the sacrum and providing a sacral-iliac connectionbetween ilium and sacrum by fixing the first end of the elongate spinalmember and the second end of the elongate connecting member relative toeach other.

Fixation of the two ends is preferably established with a connector headcomprising two holes into which the two ends are introduced and fixed.Preferably they are introduced separately and independently from eachother and preferably, the fixation of each end is also independentlyfrom the other one.

This method enables the surgeon to choose or correct for example theplacement of the iliac bone screw at a very late stage of the surgeryafter the longitudinal elements and pedicle screws have been placed init is inter-operatively decided to extend the fusion. Also other partsof the spinal fixation system can be rearranged and their relationshipto other parts can be changed within a small range at a late stage.

Further embodiments of the invention are laid down in the dependentclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described in the followingwith reference to the drawings, which are for the purpose ofillustrating the present preferred embodiment of the invention and notfor the purpose of limiting the same. In the drawings is shown

FIG. 1 a spinal fixation system according to a first embodiment of theinvention fixed on a reconstruction of a human lower spine, sacrum andilium;

FIG. 2 the fixation system according to FIG. 1 in first perspectiveview;

FIG. 3 the fixation system according to FIG. 1 in a second perspectiveview;

FIG. 4 a connector head according to the invention in a firstperspective view;

FIG. 5 the connector head according to FIG. 4 in a second perspectiveview;

FIG. 6 a side view of the connector head according to FIG. 4;

FIG. 7 a front view of the connector head according to FIG. 4;

FIG. 8 a longitudinal section of the connector head according to FIG. 4;

FIG. 9 a first perspective view of an iliac connector according to theinvention with a spinal rod arranged in the connector;

FIG. 10 a second perspective view of the iliac connector according toFIG. 9;

FIG. 11 a longitudinal section of the iliac connector according to FIG.9;

FIG. 12 a spinal fixation system according to a second embodiment of theinvention, in a first perspective view;

FIG. 13 the fixation system according to FIG. 12 in a second perspectiveview;

FIG. 14 a left side connector head according of the spinal fixationsystem according to FIG. 12 in a perspective view;

FIG. 15 a perspective view of a right side connector head for use in aspinal fixation system;

FIG. 16 a rear view of the left side connector head according to FIG.14;

FIG. 17 a side view of the left side connector head according to FIG.14;

FIG. 18 a top view of the left side connector head according to FIG. 14;

FIG. 19 a first longitudinal section view of the connector headaccording to FIG. 14 and

FIG. 20 a second longitudinal section view of the connector headaccording to FIG. 14.

DESCRIPTION OF PREFERRED EMBODIMENTS

FIGS. 1 to 3 show a first embodiment of an inventive spinal fixationsystem using an inventive iliac connector and an inventive connectorhead.

The spinal fixation system comprises one preferably two spinal rods 3extending along a spine SP and being fixed to one or more vertebrae ofthe spine SP. The spinal rod 3 is preferably curved. Known pedicle bonescrews 4 are used as anchors for the fixation to the vertebrae, whereinthese spinal bone screws 4 preferably have known tulip heads. The spinalbone screws 4 with the tulips are preferably made of titanium.

The spinal rod 3 is preferably made of a more flexible material, such asa filament composite material. Preferably it is made of carbon filamentsencapsulated in a polymer matrix, such as PEKEKK or PEEK. The compositematerial preferably comprises of about 66.6% (weight %) of carbon fibersand of about 33.3% polyether-ketoneetherketoneketone (PEKEKK) asencapsulating matrix. The fibres or filaments are preferably oriented inlayers which are parallel to each other and to a surface of the rod. Thelayers may be made up of woven first and second filaments. The firstfilaments are oriented in an axial direction of the longitudinal rod.The second filaments are oriented to perpendicular to the axialdirection. Such a material is known on the market with the name ostaPekof CoLigne AG and is described in EP 1 238 637 and US 2008/026548.

On one free end of the spinal rod 3, the last screw can be a sacral bonescrew 5 fixed to the sacrum S. It can have, as shown in this example,the same shape and size as the spinal bone screws 4. However, it canalso be different in size and/or in shape. The spinal rod 3 ispenetrating the tulip of this sacral screw 5 as well. At the penetratingend of the spinal rod 3, a connector head 1 of an inventive iliacconnector is arranged, wherein the spinal rod 3 preferably penetratesthis connector head 1 as well before ending shortly thereafter.

The total length of the spinal rod 3 and the number of spinal bonescrews 4 depend on the medical case.

Preferably, the connector head 1 is made of the same material as thescrews. Preferably, it is made of titanium.

A connecting rod 2 is held within this connector head 1 extending at anangle from the spinal rod 3. This angle is preferably approximately 90°.The connecting rod 2 can be straight or curved as well. The connectingrod 2 is quite short. Preferably, its length is between 2 and 4 cm andmore preferably about 3 cm.

The connecting rod 2 is made of a material which is more flexible thantitanium. Preferably it is made of a filament composite material likethe spinal rod 2 described above. Preferably, the spinal rod 3 and theconnecting rod 2 of a common fixation structure are made of the samematerial, preferably the one described in EP 1 238 637 and US2008/026548 and known in the market as ostPek of CoLigne AG.

The two rods 2, 3 can have the same outer geometry, especially the samediameter. Especially the connecting rod 2 has preferably a roundcross-section and it has preferably throughout its length the same outershape and the same diameter. Typical diameters are 4 to 8 mm, preferablyabout 6 mm. The connecting rod 2 can also have another cross-section,for example a polygonal one.

One free end of the connecting rod 2 penetrates the connector head 1.The other free end penetrates an anchor or fixation element which isfixed to the ilium I. Preferably, this fixation element is an iliac bonescrew 6 as best seen in FIG. 3. This screw 6 preferably has a tulip aswell. It can have the same shape and size as the sacral bone screw 5and/or the spinal bone screw 4. However it also can have a differentsize and shape. Preferably, it is not combined with a plate andpreferably it is only a single screw.

FIGS. 4 to 9 show the inventive connector head 1 in more detail. Theconnector head 1 has a generally cuboid main body wherein a transitionarea between two walls has a remarkably rounded shape and wherein anopposite wall to this transition area has an inclined section.

As can be best seen in FIG. 4, the connector head comprises two oppositeside walls 10, extending parallel to each other and being preferablyplane. A plane rear wall 11 is arranged perpendicular to these sidewalls 10 and a flat top 13 is arranged perpendicular to the side walls10 and the rear wall 11. A bottom 12 is inclined relative to the rearwall 11 and a front wall 14. Between the rear wall 11 and the bottom 12,the curved transition area 19 extends. The bottom 12 preferably hasfirst the same curvature as the transition area 19, wherein it decreasescontinuously in direction to the front wall 14.

The front wall 14 has at least to sections: an upper flat section 140extending perpendicular to the top 13 and the side walls 10 andtherefore parallel to the rear wall 11 and a lower inclined section 141extending to the bottom 12. The inclined section 141 is extendingforward and increasing the width of the connector head 1 in direction tothe bottom 12.

The directions used above, such as upper, lower, rear, front, bottom,top, refer to the orientation of the connector head 1 as shown in theFIGS. 4 to 8. They do not restrict that orientation of the connectorhead 1 when in use.

A first hole 15 is arranged in one of the side walls 10. Preferably, thefirst hole 15 is a through hole extending from one side wall 10 to theother. The first hole 15 has a first central axis 150 which extendsperpendicular to the two side walls 10 from the first side wall to thesecond one.

The first hole 15 has at its two ends a slightly non-rounded shape, ascan be best seen in FIG. 6 and FIG. 4 with reference number 151. Thishelps to fix the rod more securely within the hole. The rod ispreferably the spinal rod 3.

In the front wall 14, in particular in the inclined lower section 141, afirst fixation opening 17 is arranged, see FIG. 5. This first fixationopening 17 extends from the front wall 14 to the first hole 15 withinthe main body of the head 1, i.e. it crosses or leads into the firsthole 15. This first fixation opening 17 comprises an internal thread,allowing a first fixation screw 171 (see FIG. 11) to be screwed intothis opening 17.

A second hole 16 with a second central axis 160 extends from the rearwall 16 in direction to the front wall 14, in particular to the planeupper section 140. The second hole 16 is preferably a through hole aswell, therefore ending in the front wall 14. This second hole 16 canhave the same size and shape as the first hole 15. Preferably it has atleast the same non-rounded shape in cross-section and the same increaseddiameter at its ends. This can best be seen in FIG. 7 and FIG. 4 withreference number 161. It fixes the rod more securely within the holeThis rod is preferably the connecting rod 2.

A second fixation opening 18 is arranged in the top 13, extendingthrough the main body to the second hole 16 and is crossing it. Thesecond fixation opening 18 has an internal thread 180 as well. It haspreferably the same size as the first fixation opening 17 and it servesalso to hold a second fixation screw 181.

As can be best seen in FIG. 8, the first hole 15 and the second hole 16do not penetrate each other. Preferably, they extend in two parallelplanes, their first and second central axis 150, 160 beingperpendicular, but spaced from each other.

FIGS. 9 to 11 show the connector head 1 in use with the inventiveconnecting rod 2 and the spinal rod 3. As can be seen, each rod 2, 3, isfixed independently from each other by the first fixation screw 171 andthe second fixation screw 181 respectively. Preferably, both rods 2, 3penetrate the holes 15, 16, their ends protruding the head 1. As can beseen in FIGS. 1 and 9, the screws 171 and 181 can be fixed independentlyfrom each other and in a freely chosen chronological order.

FIGS. 12 to 20 show a second embodiment of the inventive spinal fixationsystem and second embodiments of connector heads. While the connectorhead of the first embodiment is symmetrically built and the same shapeof connector head can be used on both sides of the spine, the systemaccording to this second embodiment comprises a left side and a rightside connector head, the two heads being mirrored.

As can be seen in FIGS. 12 and 13, the only difference of the spinalsystem according to the first and this second embodiment is thedifferent kind of connector head used. This head bears in this secondembodiment the reference numbers 7, 7′ (see FIG. 15). The other elementsremain unchanged, and there reference numbers are identical with theones of the first embodiment. The description of these elements, alreadymentioned above, is therefore also applicable to this embodiment.

FIG. 14 shows a left side connector head 7, which can be used in thesystem according to FIGS. 12 and 13, i.e. on the left side of the spine.FIG. 15 shows a right side connector head 7′, which can be used with asimilar or identical system on the right side of the spine. As can beseen in comparison of FIGS. 14 and 15, the right side connector head 7′is the mirror picture of the left side connector head 7. In thefollowing, only the left side connector head 7 will be described.However, the same description also applies to the right side connectorhead 7′.

The connector head 7 of FIG. 14 is made of one single piece as a unitarypart. Preferably it is made of the same material as the screws 4mentioned above, for example it is made of titanium. The left side andthe right side connector heads 7, 7′ are similar to the one shown inFIGS. 1 to 11. The previous description of this connector head 1according to the first embodiment is therefore applicable to theseconnector heads 7, 7′ as well, where appropriate. Identical or similarfeatures, especially the ones shown in the figures, will not bedescribed in detail any more.

The connector head 7 comprises a first body 70 and a second body 74. Thefirst body 70 is also called spinal body and the second body is alsocalled connecting body. Both bodies 70, 74 have preferably a cube-likeshape. A transition area 79 is connecting the two bodies 70, 74 witheach other. The transition area 79 is preferably rounded, as can be bestseen in FIG. 18. The transition area 79 has a twisted shape, as can bebest seen in FIG. 14.

The edges of the two bodies 70, 74 are preferably rounded as well. Thebottom 72 of the connector head 7, which is preferably the bottom of thefirst body 70, can be rounded as well. These rounded parts ensure, thatno human tissue gets hurt.

The first body 70 comprises the first hole 75 and the first fixationopening 77. The second body 74 comprises the second hole 76 and thesecond fixation opening 78. At least one, preferably both holes 75, 76are through holes. The fixations openings 77, 78 comprise preferablythreads 770, 780, as can be best seen in FIGS. 19 and 20.

The first hole 75 comprises a first central axis 750 and the second hole76 comprises a second central axis 760, wherein these axis extendperpendicular but at a distance to each other; i.e. they do not crosseach other and are therefore extending in planes different from eachother.

The first body 70 is arranged below and staggered to the second body 74.They are like steps of a circular staircase. The top surface 71 of thefirst body 70 extends preferably parallel to the top surface 73 of thesecond body 74, but at a distance below it, as can be best seen in FIGS.16 and 17. The first fixation opening 77 is arranged in the top surface71 of the first body 70 and the second fixation opening 78 is arrangedin the top surface 73 of the second body 74. This means that theirthreads 770, 780 extend in the same direction, perpendicular to thecentral axis 750, 760 of the first and second holes 75, 76.

The first body 70 comprises a recess 700 which extends in direction ofthe second central axis 760 from the second hole 76 to the opposite endof the first body. This recess 700 has a rounded cross-section suitableto accommodate the connecting rod 2.

The second body 74 comprises a recess 740 which extend from the firstfixation opening 77 to the top surface 73 of the second body. Thisrecess 740 optimizes the access to the first fixation opening 77, sothat a screw can be easily entered and fixed into this first fixationopening 77.

As can be seen in FIGS. 12 and 13, this connector head 7, 7′ minimizesthe space needed for the connection of a connecting rod 2 and a spinalrod 3, but gives still independent access to both holes 75, 76 and toboth fixation openings 77, 78.

The inventive iliac connector enables a stabilization of ilium, sacrumand spine and allows at the same time movements between ilium andsacrum.

LIST OF REFERENCE SIGNS  1 connector head  10 side wall  11 rear wall 12 bottom  13 top  14 front wall 140 flat section 141 inclined section 15 first hole 150 first central axis 151 non-rounded part  16 secondhole 160 second central axis 161 non-rounded part  17 first fixationopening 170 first thread 171 first fixation screw  18 second fixationopening 180 second thread 181 second fixation screw  19 transition area 2 connecting rod  3 spinal rod  4 spinal bone screw  5 sacral bonescrew  6 iliac bone screw  7 connector head  7′ connector head  70 firstbody (spinal body) 700 first recess  71 first top surface  72 bottom  73second top surface  74 second body (connecting body) 740 second recess 75 first hole 750 first central axis  76 second hole 760 second centralaxis  77 first fixation opening 770 first thread  78 second fixationopening 780 second thread  79 transition area α angle SP Spine I Ilium SSacrum

1-22. (canceled)
 23. A spinal fixation system comprising a spinal rod,at least one spinal bone screw, at least one iliac bone screw and aniliac connector, the iliac connector comprising a connector head and aconnecting rod for connecting a sacrum or a spine to an ilium, theconnector head having a first hole having a first central axis andreceiving the spinal rod, the spinal rod penetrating the at least onespinal bone screw, and the connector head having a second hole having asecond central axis and receiving the connecting rod, the connecting rodbeing held in the at least one iliac bone screw, wherein the spinal rodand the connecting rod are made of a filament composite material, thematerial comprising a polymer matrix and the filaments being carbonfilaments encapsuled in the polymer matrix, wherein at least a firstgroup of the filaments are oriented in longitudinal direction of therods, wherein the material is more flexible than titanium, wherein thespinal rod extends in a first direction defined by the first centralaxis and the connecting rod extends in a second direction defined by thesecond central axis, wherein the first direction is different from thesecond direction and wherein the first direction and the seconddirection are at an angle to each other, and wherein the systemstabilizes spine and ilium thereby allowing some movement between iliumand sacrum.
 24. The spinal system according to claim 23, wherein thepolymer matrix is polyether-ketoneetherketoneketone (PEKEKK) orpolyetheretherketone (PEEK).
 25. The spinal system according to claim23, wherein the spinal rod and the connecting rod have throughout theirwhole length a non-changing cross-section.
 26. The spinal systemaccording to claim 23 wherein the system stabilizes spine and iliumthereby allowing some movement between ilium and sacrum.
 27. The spinalfixation system according to claim 23, wherein the spinal rod and theconnecting rod are made of the same material.
 28. The spinal systemaccording to claim 23 wherein the first central axis and the secondcentral axis extend perpendicular to one another, wherein the first holeis in communication with the first fixation opening and the second holeis in communication with the second fixation opening and wherein thefirst and second fixation openings being arranged such they allowmounting of the spinal rod and the connecting rod independently fromeach other.
 29. The spinal fixation system of claim 23 wherein theconnector head further has a first fixation opening for holding a firstfixation screw and a second fixation opening for holding a secondfixation screw, the first fixation opening leading to the first hole inorder to hold the spinal rod received in the first hole with the firstfixation screw and the second fixation opening leading to the secondhole in order to hold the connecting rod received in the second holewith the second fixation screw, wherein the first fixation opening has athird central axis extending perpendicular to the first central axis ofthe first hole and the second fixation opening has a fourth central axisextending perpendicular to the second central axis of the second hole.30. The spinal system of claim 23, wherein the fixation opening of thefirst hole is arranged at an angle different from 90° to the fixationopening of the second hole.
 31. The spinal system of claim 30, whereinthe angle is between 70° to 30°.
 32. The spinal system of claim 30,wherein the angle is between 60° to 40°.
 33. The spinal system of claim30, wherein the angle is about 60° or 45° or less than 45°.
 34. Thespinal system of claim 30, wherein the angle is 0°.
 35. The spinalsystem of claim 23, wherein the connector head comprises two side walls,a rear wall, a front wall, a bottom and a top, wherein the first hole isarranged at least in one of the side walls, the second hole is arrangedat least in the rear wall, the first fixation opening is arranged in thefront wall and the second fixation opening is arranged in the top. 36.The spinal system of claim 35 wherein the front wall comprises at leastone section which is inclined with respect to the rear wall and whereinthe first fixation opening is arranged in the inclined section.
 37. Thespinal system of claim 35 wherein a transition area connects the rearwall and the bottom and wherein this transition area is rounded.
 38. Thespinal system of claim 23 wherein the first fixation opening is arrangedin a first surface of the connector head and the second fixation openingis arranged in a second surface of the connector head, wherein the firstsurface extends in a plane parallel but at a distance to a plane definedby the second surface.
 39. The spinal system of claim 23 wherein theconnector head comprises a first body with a cube-like shape and asecond body with a cube-like shape, the first body comprising the firsthole and the first fixation opening and the second body comprising thesecond hole and the second fixation opening, wherein the first body isarranged staggered below the second body.
 40. The spinal system of claim23 wherein and least one of the first and the second hole is a throughhole.
 41. The spinal fixation system of claim 23 wherein the second axisis extending at an angle of 84° to the first central axis.
 42. Thespinal fixation system of claim 23 wherein the second axis is extendingat an angle of 90° to the first central axis.
 43. The spinal fixationsystem of claim 23 wherein the third central axis and the fourth centralaxis extend parallel to one other.
 44. A method for stabilizing a spine,the method comprising the steps of accessing the sacrum and iliacportions of the spine; fixing a spinal rod with at least one spinal bonescrew to at least one pedicle of the spine, the spinal rod having afirst end; fixing a connecting rod with a iliac bone screw to the iliac,the connecting rod having a second end and fixing the first end of thespinal rod and the second end of the connecting rod relative to eachother at an angle of about 90°, wherein the chronology of fixation ofthe first end the second end can be chosen by the surgeon.
 45. Themethod of claim 44, further comprising the step of fixing the spinal rodwith at a sacral bone screw to the sacrum and providing a sacral-iliacconnection between ilium and sacrum by fixing the first end of thespinal rod and the second end of the connecting rod relative to eachother.